Find all Key-Elements by the same Value in Dicts

Question

I have question about Dictionaries in Python.

here it is:

I have a dict like dict = { \'abc\':\'a\', \'cdf\':\'b\', \'gh\':\'a\', \'fh\':\'g\', \'hfz\'

Answer 1

If you do specifically want tuples as the values in your new dictionary, you can still use defaultdict, and use tuple concatenation. This solution works in Python 3.4+:

from collections import defaultdict

source = {'abc': 'a', 'cdf': 'b', 'gh': 'a', 'fh': 'g', 'hfz': 'g'}
target = defaultdict(tuple)

for key in source:
    target[source[key]] += (key, )

print(target)

Which will produce

defaultdict(, {'a': ('abc', 'gh'), 'g': ('fh', 'hfz'), 'b': ('cdf',)})

This will probably be slower than generating a dictionary by list insertion, and will create more objects to be collected. So, you can build your dictionary out of lists, and then map it into tuples:

target2 = defaultdict(list)

for key in source:
    target2[source[key]].append(key)

for key in target2:
    target2[key] = tuple(target2[key])

print(target2)

Which will give the same result as above.